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Discuss Diversity in the Electrical Wiring, Theories and Regulations area at

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  1. bigd

    bigd Active EF Member

    Dear All,

    I am trying to calculate diversity for an installation. The DB has a 60A main fuse. TT system. Small 2 bedroom cottage. Unable to get converted to TNS

    At the present time I have the following circuits
    Up ring 32A MCB (2 Bedrooms)
    Down ring 32A MCB (Small lounge & dining room)
    Up lights 6A MCB (4 x 60W bulbs)
    Down lights 6A MCB (4 x 60W Bulbs)
    Immersion 16A dedicated circuit (13A fused spur/switch) 2.4kW
    Air source pump 40A (nominal 15A but has potential of high start current if temp below 0 deg C)
    Airsource control 6A dedicated circuit

    Adding all this up, even with diversity, is well in excess of the 60A main fuse. Is there anything I can do to reduce the diversity of this installation?

    It may be worth noting the following:
    1. That the immersion is a back up if the air source heater fails
    2. Both ring circuits will be subject to very light loads

    Cheers Dave
  2. widdler

    widdler Forum Mentor

    North East

    I've not done any number crunching, but if the immersion is only able to be energised when the air source pump fails, and if the air source pump truly is 15A nominal, I get around 54A.
  3. Engineer54

    Engineer54 Guest

    It'll probably struggle to see even that 54A me thinks!!!!
  4. Archy Styrigg

    Archy Styrigg Forum Mentor

    I get 40A, and that's being generous.

    For your pump, give it a C breaker to cover that.
    Last edited: Feb 17, 2012
  5. widdler

    widdler Forum Mentor

    North East
    Most likely, with ring finals.
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